The invention relates to a ram air channel arrangement for ambient air supply into an aircraft and a method for operating such a ram air channel arrangement.
Ram air channels are used in modern aircraft for supplying various systems located on board the aircraft, such as, for example, an air conditioning system, with ambient air from the aircraft environment. Such ram air channels comprise an air inlet having a ram air inlet channel extending downstream of the air inlet, a ram air channel active portion extending downstream of the inlet channel and a ram air outlet channel extending downstream of the ram air channel active portion and having an air outlet at its downstream end. In the ram air channel active portion there may be arranged, for example, a heat exchanger of an air conditioning system of the aircraft, which is cooled by the cold ambient air flowing through the ram air channel During the flight, owing to the ram pressure which builds up in the ram air channel, ambient air flows through the air inlet into the ram air inlet channel and the ram air channel active portion, whereas when the aircraft is on the ground, mechanical devices, such as, for example, injectors or fans arranged in the ram air channel, are used for generating an ambient air flow through the ram air channel. Heated ambient air leaves the ram air channel through the ram air outlet channel.
In order to enable the ambient air flow supplied through the ram air channel to adapt to the ambient air requirement of the systems supplied with the ambient air, there is usually arranged in a region of the air inlet and in a region of the air outlet of the ram air channel in each case at least one movable element which allows, respectively, an enlargement and a diminution or a complete closure of the flow cross-section of the air inlet and of the air outlet.
In today's modern passenger aircraft, the ram air inlet channel is predominantly provided with an NACA (National Advisory Committee for Aeronautics) inlet arranged in the region of the aircraft outer skin and comprises a first and a second inlet flap which can be adjusted by a common actuator. When, in flight, the first and the second inlet flap are moved from a position closing the ram air inlet channel into an open position by actuation of the actuator, ambient air flows through the air inlet into the ram air inlet channel A conventional ram air outlet channel is equipped with an adjustable outlet flap, by which the ambient air flowing through the ram air channel is released to the aircraft environment. In dependence on the position of the inlet flaps and of the outlet flap which free the flow cross-section at the inlet and outlet of the ram air channel, the ambient air mass flow through the ram air channel can be set.
From DE 10 2009 017 040 A1 or U.S. Pat. No. 8,262,018 B2 there is known a method for controlling the inlet flaps and the outlet flaps of a ram air channel, which enables a minimization of the aerodynamic losses caused by the ram air channel.